# 3 12 12 triangle

### Acute isosceles triangle.

Sides: a = 3   b = 12   c = 12

Area: T = 17.85988213497
Perimeter: p = 27
Semiperimeter: s = 13.5

Angle ∠ A = α = 14.36215115629° = 14°21'41″ = 0.25106556623 rad
Angle ∠ B = β = 82.81992442185° = 82°49'9″ = 1.44554684956 rad
Angle ∠ C = γ = 82.81992442185° = 82°49'9″ = 1.44554684956 rad

Height: ha = 11.90658808998
Height: hb = 2.97664702249
Height: hc = 2.97664702249

Median: ma = 11.90658808998
Median: mb = 6.36439610307
Median: mc = 6.36439610307

Inradius: r = 1.32328756555
Circumradius: R = 6.04774315681

Vertex coordinates: A[12; 0] B[0; 0] C[0.375; 2.97664702249]
Centroid: CG[4.125; 0.99221567416]
Coordinates of the circumscribed circle: U[6; 0.7565928946]
Coordinates of the inscribed circle: I[1.5; 1.32328756555]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 165.6388488437° = 165°38'19″ = 0.25106556623 rad
∠ B' = β' = 97.18107557815° = 97°10'51″ = 1.44554684956 rad
∠ C' = γ' = 97.18107557815° = 97°10'51″ = 1.44554684956 rad

# How did we calculate this triangle?

Now we know the lengths of all three sides of the triangle and the triangle is uniquely determined. Next we calculate another its characteristics - same procedure as calculation of the triangle from the known three sides SSS. ### 1. The triangle circumference is the sum of the lengths of its three sides ### 2. Semiperimeter of the triangle ### 3. The triangle area using Heron's formula ### 4. Calculate the heights of the triangle from its area. ### 5. Calculation of the inner angles of the triangle using a Law of Cosines ### 6. Inradius ### 7. Circumradius ### 8. Calculation of medians #### Look also our friend's collection of math examples and problems:

See more informations about triangles or more information about solving triangles.